Accidents and complaints caused by poor quality of food are reported on a daily basis, and consumers' eyes on food are still severe. In particular, although it is difficult to identify the factors that cause complaints, such as the variety of odor expressions of the declarants, the lack of official laws and clear classification standards such as food poisoning, and the tendency of the causative substances to volatilize and disappear, there are not many studies that systematically arrange the actual conditions and derive knowledge that contributes to the identification of the process of generating offensive odors. In this study, we collected cases of food odor complaints over the past 40 years, classified them from four viewpoints: causative food, odor, causal process, and flow diagram (FD) evaluation, and arranged individual complaint cases. We attempted to quantify and discuss the identification rate of the causative process from the viewpoint of odor classification by hazard analysis and flow diagram analysis based on the HACCP viewpoint. As a result, we successfully found that conducting process investigations based on flow diagram analysis can lead to the identification of odor-causing processes.